The present invention relates to a printed circuit board, and more particularly, to a printed circuit board which can improve the mounting reliability of a warped semiconductor chip.
A typical wafer is provided with hundreds to several thousands of semiconductor chips on which the same electrical circuits are printed. Electrical connections are formed so that the semiconductor chips can transmit and receive signals to and from an external means. Also, the semiconductor chips are sealed with an encapsulating mold so that the chips can withstand external shocks. A semiconductor chip with electrical connections and an encapsulating mold may be referred to as a semiconductor package, and such semiconductor packages can be manufactured to perform specified functions and to have a predetermined physical shape.
Even as electronic/electric products have become more highly functionalized, the volume of electronic terminals have been decreased, and the weights thereof have been reduced. Therefore, in order to meet the requirements toward light weight, slimness, compactness and miniaturization, the thin formation and high density mounting of a semiconductor package have been regarded as important factors.
Currently, in computers, notebooks, mobile phones, etc., while the capacity of a chip such as RAM (random access memory) and flash memory has been increased to satisfy memory capacity requirements, the trend toward miniaturization of a package has become prominent. Thus, the demand for a thin, light and compact semiconductor package which would accommodate this trend has abruptly increased.
In order to manufacture a thin semiconductor package, it is necessary to reduce the thickness of the semiconductor chip contained therein. However, limitations necessarily exist in reducing the thickness of a semiconductor chip. One main problem is caused during singulation when, after the back surface of a wafer is back-grinded, the semiconductor chips becomes warped in the course of manufacturing individual semiconductor chips by sawing the wafer and bonding semiconductor chips to a printed circuit board. Due to warpage, the mounting reliability of the semiconductor chips is degraded, and the manufacturing yield is decreased.
FIG. 1 is a view explaining such a problem.
Referring to FIG. 1, in the course of mounting a semiconductor chip 20 onto a printed circuit board 10, due to the curved shape of the warped semiconductor chip 20, bumps 21 located at the center portion A of the semiconductor chip are raised resulting in poor junctions. Further, at the edge portion B of the semiconductor chip 20, bumps 21 are overly compressed whereby signal lines are more apt to be short-circuited when the pitch is narrow. As a result, the mounting reliability of a semiconductor chip is degraded and the manufacturing yield is decreased.